The present disclosure relates to digital printing systems where flexibility is desired for printing both monochromatic and color prints on sheet stock and where it is desired to employ more than one print engine operating on a given print job and to provide the flexibility of simplex or duplex printing. Systems of this type require flexibility in varying the path of the sheet stock to enable the use of plural print engines either in tandem or in parallel and to provide duplex printing. Thus, various combinations of inverters and transporters are required to feed sheet stock through the unit to accomplish the desired printing function. Heretofore, in order to provide the desired printing flexibility, the machine or system was built up of the various components such as inverters, transporters, marking engines, fusers and finishers in order to provide a particular desired combination of printing capability; and, the components were built up or assembled on a frame and housed in a cabinet to provide the completed machine. As the desired flexibility and combinations of printing capability were increased, the number of components assembled onto the frame disposed within the cabinet increased. The complexity of interconnecting the various components and the controls for a desired machine configuration has resulted in relatively expensive equipment which has limited the marketability of the systems relative to the desired capabilities.
Thus, it has been desired to find a way to provide the desired complex printing functions for which modern digital printers are capable and to provide such multi-function capacity in a machine that was relatively low in manufacturing cost yet reliable and robust in service.